1. Field of the Invention
This invention relates to a method of making magnetic particles adapted for use in the production of magnetic recording media, such as audio, video and like tapes, and more particularly to a method of making magnetic substances composed principally of cobalt which are uniform in particle size and excellent in magnetic properties.
2. Description of the Prior Art
It is already known to the art, for example, in IBM Technical Disclosure Bulletin vol. 9, No. 3, August 1966, page 320, to add a small amount of palladium chloride solution with its pH adjusted either to a solution containing cobalt ions, or to a solution containing cobalt ions and nickel ions, to heat the resulting solution up to a temperature close to its boiling point in the presence of a reducing agent, such as sodium hypophosphite, and to form, as a magnetic powder, a precipitate resulting from the ensuing chemical reaction.
However, the magnetic particles composed principally of cobalt, thus obtained, are almost non-uniform in particle size, and also are not well dispersed. Therefore, it is difficult to obtain magnetic particles of this composition having uniform size and shape, and hence having the excellent magnetic characteristics which are required for magnetic recording media.
The U.S. Pat. No. 3,607,216 and certain other prior art suggests that a viscosity improver containing gelatin can be added to the reducing agent to improve the viscosity of the magnetic powder, thereby to reduce the particle size thereof.
There has now been discovered a new and very useful process for making cobalt-type magnetizable particles in which, in place of gelatin, one employs a protein such as albumin or hemoglobin.